A conventional, storable bipropulsion system uses a hydrazine (e.g., monomethylhydrazine) as the fuel component. This fuel affords useful performance characteristics and has a fast ignition with the oxidizer. This fast (hypergolic) ignition provides system reliability for on-demand action of the propulsion system. The conventional, storable bipropulsion system is limited by its inherent energy density that can be traced, in large measure, to the density of the fuel. Also, there are significant costs and operational constraints associated with handling the fuel that derives from the fuel's very toxic vapor.
The challenge is made more difficult since the fuel/oxidizer combination is desired to be hypergolic. Hypergolicity is defined as self ignition that occurs within milliseconds after contact of fuel with oxidizer, herein “fast ignition”. Hypergolic ignition is valuable because it offers high reliability, eliminates the inert mass of a separate ignition system, and provides an ability to restart for missions that require multipulse operation.
Accordingly, there is need and market for hypergolic bipropellants that overcome the above prior art shortcomings.
There has now been developed ionic hypergolic bipropellant fuels of reduced toxicity, as also described below.